Implantable electronic devices are in use providing electronic pulses to stimulate tissue via a lead extending from an implanted pulse generator to a desired internal location. An example of this type of technology is a pacemaker and a pacing lead which provides electrical stimulation to the heart. The pacemaker is usually implanted in a subcutaneous cavity, and the leads extend either transvenously to the internal cavities of the heart, or to patch electrodes located on external surface of the heart.
The leads generally include at least one and often two or more electrodes located at a distal end, and a connector having a similar number of electrical connector elements for interconnection to the pulse generator at the proximal end. The electrical connector elements at the proximal end and the distal electrodes are interconnected by conductors extending through an insulated lead body. It is common for the leads to include helically wound conductors which are either coaxially mounted or side-by-side wound within the lead body, separated by insulation.
The connector is inserted into a receiving orifice in a header portion of the pulse generator. The header portion of the pulse generator may be formed from an epoxy material which is assembled and bonded to the main body of the pulse generator. The main body of the pulse generator is generally a metallic self-contained housing or can, which encloses the source of electrical energy and electrical circuitry for controlling the electrical stimulus delivered by the lead.
In the design of the lead connector and the pulse generator, it is important for the lead to be safely secured to the pulse generator to prevent inadvertent decoupling. Generally, connectors have been assembled using flexible insulation materials to separate the respective electrical components. Problems which arise in the construction and use of multiple conductor lead connectors are primarily related to the design of the electrical interconnection between the conductors and the contacts. The connector must be constructed in a manner which prevents fluids from invading the connector and shorting the electrical conductors therein.
One inherent physical weakness of small pacemaker lead connectors (i.e. VS-1 and IS-1 standard) is bond failure between conductor and insulation laminations. Traditional coaxial connectors transmit most mechanical stress between material layers during tensile or torsional loading. Present lead designs rely on chemical bonds between these layers to withstand this stress. Bonding or molding of traditional lead construction is very process sensitive and can be weakened by assembly process contamination or can fail after implant due to hydrolyzation of the bond interface.
It would be beneficial to have a lead assembly including a connector assembly featuring an improved structural interconnection between the conductors and the electrical connectors, and having increased resistance to failures from invasion of fluids.